1. Field of the Invention
The present invention relates generally to friction clutches, and more specifically, to a friction clutch that automatically adjusts to maintain a desired clutch release load requirement and that compensates for the wear of various parts thereof, including the clutch disc.
2. Description of the Related Art
In a known friction clutch arrangement of the type that is not automatically adjustable, the release force required to disengage the clutch changes over the life of the clutch. As the friction surfaces of the clutch disc and other parts of the clutch become worn, the relative position of the pressure plate changes with respect to the diaphragm spring.
These changing relationships coupled with the characteristics of an axially stressed diaphragm spring typically cause the release force required to disengage the clutch to increase over time. If the clutch is not adjusted to compensate for the relative movement of the fulcrums, the release force required to disengage the clutch will increase to a point at which the clutch may be rendered unusable by some individuals.
Consequently, the wearing of the friction surfaces in a clutch arrangement results in a varying release force requirement over the life of the clutch, in addition to limiting the life of the clutch arrangement. Additionally, in known clutch arrangements that do not adjust automatically, the thickness dimension of the clutch disc is critical to the proper operation of the clutch. This results in manufacturing requirements that are costly and difficult to achieve.
The prior art references has endeavored to overcome the above-referenced problems by providing self-adjusting clutches. In one known arrangement, a self-adjusting mechanism for a friction clutch employs a sensing mechanism that detects a decrease in the free travel distance of a release yoke between engaged position and a disengaged positions. An adjustment device responsive to the sensing mechanism causes an adjusting ring to compensate for the decrease in the free travel distance traveled by the release yoke.
In a further known arrangement, an automatically adjustable friction clutch employs a compensating means disposed between a housing and a diaphragm spring. The adjustable clutch includes a biasing element that provides a supporting force that causes the diaphragm spring to engage a seat. The diaphragm spring remains tiltable about the seat and its position with respect thereto is shifted to maintain a constant release force.
Other known arrangements employ wedge mechanisms wherein the inclined surfaces thereof extend along the circumference of a spring and provide adjustment to maintain the posture of the spring. Additionally, a clutch cover assembly including a movement regulation mechanism and a moveable support member have been employed to compensate for the displacement associated with the wear of a friction member.
Although the aforementioned known self-adjusting clutches have overcome some of the problems associated with the previously mentioned non-adjustable clutches, there is still a need for improved adjustable mechanisms for clutches. Specifically, there is a need for a self-adjusting clutch that provides greater flexibility in positioning an adjustment means. This increased flexibility facilitates clutch model design and manufacture. There is also a need for a self-adjusting clutch that provides greater stability and precision regarding the operation of the diaphragm spring. Such increased stability would improve the actuation characteristics of the clutch system.